IEEE C57.116:1989 pdf download.IEEE Guide for Transformers Directly Connected to Generators.
This guide describes selection and application considerations for the unit transformer and unit auxiliaries transformer. Consideration is given to connections that include direct connection and connections through generator breakers and load break switches. The considerations referred to in this guide apply to hydroelectric and thermal electric generating stations. Various transformer connections and possible operating problems under normal and abnormal conditions are treated.
Phasing procedures, basic impulse insulation level selection, and loading practices are not covered.
1.2 References
This guide shall he used in conjunction with the following publications:
[1] ANSI C50. 13-1977, American National Standard Requirements for Cylindrical Rotor Synchronous Generators.
[2] ANSI C57.12.30-1977, American National Standard Load-Tap-Changing Transformers 2300(M) Volts and Below
3750/4687 Through 6() (MM)/8() 000/lW) (MX) kVA, Three Phase.
[3] ANSI C57. 12.70-1978 (R 1987), American National Standard Terminal Markings and Connections for Distribution and Power Transformers.
[4] ANSI C84. 1-1982, American National Standard Voltage Ratings for Electric Power Systems and Equipment.
[5] ANSI C92.2-1987, American National Standard Power Systems —Alternating-Current Electrical Systems and Equipment Operating at Voltages above 230 Kilovolts Nominal—Preferred Voltage Ratings.
[6] ANSI/IEEE Std 100-1988 IEEE Standard Dictionary of Electrical and Electronics Terms.
[7] ANSI/IEEE Std 505-1977 IEEE Standard Nomenclature for Generating Station Electric Power Systems.
[8] ANSI/IEEE C57. 12.00-1987 IEEE Standard General Requirements for Liquid-Immersed Distribution, Power, and Regulating Transformers.
2. Definitions
The definitions listed below are in accordance with ANSI/IEEE Std l(X)-19g8 161 and ANSI/IEEE Std 505-1977 171.
generator (rotating machinery): A machine that converts mechanical power into electrical power.
station service transformer (SST): A transformer that supplies power from a station high-voltage bus to the station auxiliaries and also to the unit auxiliaries during unit startup and shutdown or when the unit auxiliaries transformer is not available or both.
unit: The generator or generators. associated prime mover or movers, auxiliaries, and energy supply or supplies that are normally operated together as a single source of electric power.
unit auxiliaries transformer (UAT): A transformer intended primarily o supply all or a portion of the unit auxiliaries.
unit transformer (UT): A power system supply transformer that transforms all or a portion of the unit power from the unit to the power system voltage.
3. Introduction
The unit-connected generating system came into usage as generator size and generator bus fault current levels began to exceed the capability of breakers that were available to isolate the generator from the power system. Generally, the generator auxiliaries load is fed from a transformer that is connected directly to the generator bus. An alternate source of power is normally supplied from the transmission system by a second transformer during unit startup, shutdown, and other contingencies. Such a system is shown in Fig I. Typically, an isolated phase bus is used for connection between ihe generator and its UT and UAT: thus, the system is unit connected.IEEE C57.116 pdf download.